A transmission device that is mounted on a mobile terminal amplifies a modulation signal and radio-transmits the modulation signal. According to a communication method, the transmission device changes a transmission power if desired.
The transmission device includes an amplifying unit, which amplifies a modulation signal, and a level detecting unit, which detects an output power of the amplifying unit. The transmission device includes a unit that controls the output power of the amplifying unit according to the output of the level detecting unit. Based on the output of the level detecting unit, the control unit adjusts the strength of the modulation signal that is to be input into the amplifying unit.
In recent years, there has been various communication methods, and there is a transmission device that performs transmission of a plurality of several communication methods and frequency bands. In most cases, the level detecting unit is formed with a filter that removes a waved high frequency component that is rectification-detected with a diode that rectification-detects the output of the amplifying unit. Therefore, an input impedance as an impedance corresponding to the input of the level detecting unit includes a frequency property. As a result, even if the output power value of the amplifying unit as a detection target of the level detecting unit is equivalent to the output power value of the level detecting unit, the output of the level detecting has a different value if the frequency bands are different from each other.
Japan Laid-open Patent Publication No. 2007-266758 and Japan Laid-open Patent Publication No. 2000-341142 disclose a technique for adjusting an output of the level detecting unit in a case where the communication method is switched.
The above-described transmission device stores a correspondence relation between the output power of the amplifying unit and the output of the level detecting unit for each communication method. Based on the stored content, the above-described transmission device may correspond to a relation between the output of the level detecting unit and the transmission output.
However, the transmission device has an individual difference of the amplifying unit. If the above-described method is employed, the transmission device measures the correspondence relation between the transmission output and the output of the level detecting unit, respectively, at the shipping time. Each operation is typically performed by the transmission device to store each of the values. In particular, the transmission device corresponding to the above-described communication methods stores measurement results of the correspondence relation between the transmission output and the level detecting unit in the range of the assumed transmission output in the storage unit, so that the operation procedures are increased.
An aspect of the present invention is to provide a transmission device that is able to simplify the adjustment of the output power at the shipping even though the transmission device may correspond to the plurality of communication methods.